\begin{tikzpicture}[
    river/.style={decorate, decoration={random steps,segment length=3pt,amplitude=2pt}},
]
    \tkzDefPoints{0/0/A, 4.5/0/B}
    \tkzDefTriangle[two angles=55 and 65](A,B)  \tkzGetPoint{C}
    \tkzDrawSegment[thick](A,B)
    \tkzDrawSegments[dashed](A,C  B,C)
    \tkzLabelPoints[left](A)
    \tkzLabelPoints[right](B)
    \tkzLabelPoints[above](C)

    \begin{scope}[yshift=1.1cm]
        \foreach \x in {1, ..., 5} {
            \coordinate (X) at (0, \x/5);
            \draw [river]
                (X) to [out=10, in=160] +(2.5, -0.1)
                to [out=10, in=170] +(5, 0.3);
        }
    \end{scope}
\end{tikzpicture}

